Process for the recovery of value metals from material containing base metal oxides

Abstract

A process for leaching a value metal from oxidic materials, such as a lateritic nickel ore, comprising the step of leaching the ore with a lixiviant comprising a cationic salt (e.g., magnesium chloride) and hydrochloric acid is disclosed. An oxidant or additional metal chloride (such as that which results from the leaching operation) may be added. In one embodiment, the process comprises recovery of a value metal from ore comprising the steps of: leaching the ore with a lixiviant; separating a value metal-rich leachate from the ore in a first solid-liquid separation; oxidizing and neutralizing the value metal-rich leachate so obtained; and separating a solution of magnesium chloride from the leachate so obtained in a second solid-liquid separation. In another embodiment, the lixiviant solution is regenerated from the solution of magnesium chloride. In a further embodiment, regeneration of the lixiviant solution includes a step of producing magnesium oxide from the solution of magnesium chloride.

1. A process for treating a lateritic nickel ore containing at least one base metal oxide in which the lateritic nickel ore is leached at a pH less than 3 with a lixiviant comprising hydrochloric acid and at least one chloride salt containing cations having a higher hydration number than hydrogen to produce a leachate, the concentration of chloride ions is above about 4.5 moles of total chloride/liter of lixiviant and the molar ratio of cations having a higher hydration number than hydrogen to the amount of hydrochloric acid in the lixiviant is from about 0.15 to about 4.5. 
     
     
       2. The process as claimed in  claim 1  wherein the cation is selected from the group consisting of alkali metals, alkaline earth metals, ferric iron, ferrous iron, cuprous copper, cupric copper and mixtures thereof. 
     
     
       3. The process as claimed in  claim 1  wherein the cation is selected from the group consisting of sodium, calcium, potassium, lithium, magnesium, ferric iron, ferrous iron, cuprous copper, cupric copper and mixtures thereof. 
     
     
       4. The process as claimed in  claim 1  wherein, prior to contacting the lateritic nickel ore, the cation consists essentially or magnesium. 
     
     
       5. The process as claimed in  claim 1  wherein at the end of the leaching step, at least 25 weight % of the cation is magnesium. 
     
     
       6. The process as claimed in  claim 1  wherein the concentration of chloride ions is from 4.5 to 14M. 
     
     
       7. The process as claimed in  claim 1  wherein the concentration of chloride ions is from 6 to 12M. 
     
     
       8. The process as claimed in  claim 1  wherein the molar ratio of cations in the lixiviant to the amount of HCl in the lixiviant is from about 0.3 to about 2.5. 
     
     
       9. The process as claimed in  claim 1  wherein the lateritic nickel ore comprises more than 25 weight percent iron and the molar ratio of cations in the lixiviant to the amount of HCl in the lixiviant is from about 0.15 to about 3. 
     
     
       10. The process as claimed in  claim 1  wherein the lateritic nickel ore comprises more than 25 weight percent iron and the molar ratio of cations in the lixiviant to the amount of HCl in the lixiviant is from about 1 to about 2.3. 
     
     
       11. The process as claimed in  claim 1  wherein the lateritic nickel ore comprises less than 25 weight percent iron and the molar ratio of cations in the lixiviant to the amount of HCl in the lixiviant is from about 0.3 to about 2. 
     
     
       12. The process as claimed in  claim 1  wherein the lateritic nickel ore comprises less than 25 weight percent iron and the molar ratio of cations in the lixiviant to the amount of HCl in the lixiviant is from about 0.15 to about 2.3. 
     
     
       13. The process as claimed in  claim 1  wherein the lateritic nickel ore comprises an oxidic base metal ore. 
     
     
       14. The process of  claim 1  in which the leach is carried out at a temperature in the range of from about 75° C. to the boiling point of the lixiviant. 
     
     
       15. The process of  claim 1  in which the leach is carried out at a temperature in the range of from about 100° C. to the boiling point of the lixiviant. 
     
     
       16. The process of  claim 1  wherein the process is conducted in an unpressurized vessel. 
     
     
       17. The process of  claim 1  wherein the Eh is sufficiently low to maintain base metals in the lixiviant in a divalent state and sufficiently high to maintain iron as ferric iron. 
     
     
       18. The process of  claim 1  wherein the Eh is in the range of 300 to 700 mV. 
     
     
       19. The process of  claim 1  wherein the Eh is in the range of 350 to 600 mV. 
     
     
       20. The process of  claim 1  wherein the pH of the lixiviant at the start of the leach is up to about 0.4, and the pH of the lixiviant increases during the leaching step to the range 0.4-2.5 to precipitate iron and maintain a nickel rich leachate, as measured by conventional instrumentation. 
     
     
       21. The process of  claim 4  wherein the pH of the lixiviant at the start of the leach is up to about 0.5, and the pH of the lixiviant increases during the leaching step to the range 0.7-2.5 to precipitate iron and maintain a nickel rich leachate, as measured by conventional instrumentation. 
     
     
       22. The process of  claim 20  wherein the leachate has solublized therein a first metal comprising at least one member selected from the group consisting of, copper, aluminum, zinc and chromium and a second metal comprising at least one member selected from the group consisting of nickel and cobalt and the process further comprises:
 (a) separating a value metal-rich leachate from the lateritic nickel ore in a first solids/liquid separation; 
 (b) increasing the pH of the leachate to obtain a solid fraction containing at least a portion of the first metal and a first metal-depleted leachate, and separating the solid fraction from the first metal-depleted leachate in a second solids/liquid separation step; 
 (c) further increasing the pH of the first metal-depleted leachate to obtain a second metal depleted leachate and a solid fraction containing the second metal as a precipitated hydroxide, and separating the solid fraction containing the second metal from the second metal-depleted leachate in a third solids/liquid separation step. 
 
     
     
       23. The process of  claim 22  wherein the leachate also has solublized therein at least one of iron and manganese and step (b) further comprises subjecting the value metal-rich leachate to oxidation. 
     
     
       24. The process of  claim 22  wherein the leachate also has solublized therein iron and step (b) further comprises treating the value metal-rich leachate to convert ferrous iron to ferric iron. 
     
     
       25. The process of  claim 22  wherein the leachate also has solublized therein manganese and step (b) further comprises treating the value metal-rich leachate such that the manganese is in its tetravalent state. 
     
     
       26. The process of  claim 22  wherein the cation comprises magnesium and the second metal-depleted leachate is subjected to recycle steps for recovery of magnesium chloride and hydrochloric acid. 
     
     
       27. The process of  claim 22  wherein, prior to contacting the lateritic nickel ore, the cation is magnesium and the second metal-depleted leachate is treated to produce a solution comprising magnesium chloride and hydrochloric acid that is used as the lixiviant. 
     
     
       28. The process of  claim 27  wherein the treatment step of  claim 27  also produces magnesium oxide. 
     
     
       29. The process of  claim 28  wherein at least some of the magnesium oxide is used as a pH adjustment agent in at least one of steps (b) and (c). 
     
     
       30. The process of  claim 29  in which treatment step includes partial evaporation and hydrolysis. 
     
     
       31. The process of  claim 1  in which the lixiviant comprises hydrochloric acid, magnesium chloride and at least one member selected from the group consisting of (i) at least one additional metal chloride which is added to the lixiviant prior to the lixiviant contacting the lateritic nickel ore; (ii) at least one additional cation which is leached from the lateritic nickel ore and (iii) an oxidant. 
     
     
       32. The process of  claim 22  in which additional metal chloride or an additional cation is present. 
     
     
       33. The process of  claim 32  in which the additional metal chloride is at least one member selected from the group consisting of sodium chloride, potassium chloride, calcium chloride, copper chloride and iron chloride. 
     
     
       34. The process of  claim 33  in which the amount of additional metal chloride and cation is 1-25 wt. % of the amount of magnesium chloride. 
     
     
       35. The process of  claim 31  in which an oxidant is present. 
     
     
       36. The process of  claim 35  in which the oxidant is at least one member selected from the group consisting of air, oxygen, chlorine, hypochlorite, chlorite, chlorate, perchlorate, permanganate and peroxide. 
     
     
       37. The process of  claim 31  in which additional metal chloride and oxidant are present. 
     
     
       38. The process of  claim 37  in which the additional metal chloride is at least one member selected from the group consisting of sodium chloride, potassium chloride, calcium chloride, copper chloride and iron chloride and an oxidant is at least one member selected from the group consisting of air, oxygen, chlorine, hypochlorite, chlorite, chlorate and hydrogen peroxide. 
     
     
       39. The process of  claim 32  in which at least a portion of one of the first metal-depleted leachate and the second metal-depleted leachate is treated to regenerate the lixiviant by admixing a magnesium chloride solution with gaseous hydrogen chloride. 
     
     
       40. The process of  claim 39  in which the portion of one of the first metal-depleted leachate and the second metal-depleted leachate is subjected to distillation for separation of azeotropic hydrochloric acid. 
     
     
       41. The process of  claim 40  in which the gaseous hydrogen chloride is admixed with the portion of one of the first metal-depleted leachate and the second metal-depleted leachate to increase the amount of hydrochloric acid separated as azeotropic hydrochloric acid. 
     
     
       42. The process of  claim 1  wherein the lateritic nickel ore is obtained from limonite and saprolite horizons. 
     
     
       43. A process for treating a lateritic nickel ore containing at least one base metal oxide comprising exposing the lateritic nickel ore to a lixiviant having a pH less than about 0.5 to produce a leachate, the lixiviant comprising hydrochloric acid and at least one chloride salt containing cations having a higher hydration number than hydrogen, the concentration of chloride ions and cations in the lixiviant is selected to leach ferric iron from the material and to hydrolyze leached iron to hematite and/or a magnetic iron oxide towards the end of the leach by increasing the pH. 
     
     
       44. The process as claimed in  claim 43  wherein the leachate contains residual amounts of iron chloride. 
     
     
       45. The process as claimed in  claim 43  wherein an amount of magnesium is leached from the lateritic nickel ore and the cation comprises magnesium and the process further comprises adjusting the concentration of magnesium in the lixiviant to control the amount of magnesium leached from the lateritic nickel ore. 
     
     
       46. The process as claimed in  claim 43  wherein the cation comprises magnesium and the process further comprises adjusting the concentration of magnesium in the lixiviant that is contacted with the lateritic nickel ore so as to minimize magnesium being leached from the lateritic nickel ore. 
     
     
       47. The process as claimed in  claim 43  wherein the concentration of cations having a higher hydration number than hydrogen is selected to reduce the activity of water in the lixiviant. 
     
     
       48. The process of  claim 43  wherein the lateritic nickel ore is exposed to the lixiviant without being subjected to a roasting step. 
     
     
       49. The process of  claim 44  wherein, prior to contacting the lateritic nickel ore, the lixiviant consists essentially of magnesium chloride and hydrochloric acid. 
     
     
       50. The process of  claim 43  wherein the lateritic nickel ore is obtained from limonite and saprolite horizons. 
     
     
       51. The process of  claim 43  further comprising subjecting the leachate to a first solid/liquid separation step after the pH is increased. 
     
     
       52. A process for treating a lateritic nickel ore containing at least one base metal oxide comprising exposing the lateritic nickel ore to a lixiviant having a pH less than about 0.5 to produce a leachate, the lixiviant comprising hydrochloric acid and at least one chloride salt containing cations having a higher hydration number than hydrogen, and adjusting the Eh of the lixiviant at the end of the leaching step such that the Eh is sufficiently low to maintain base metals in the lixiviant in a divalent state and the Eh, pH and temperature are sufficiently high and the amount of free water is sufficiently low to precipitate iron as hematite and/or a magnetic iron oxide form. 
     
     
       53. The process of  claim 52  wherein the Eh is sufficiently high such that iron chloride that forms during the leach is precipitated as hematite and/or magnetic iron oxide by appropriately adjusting the pH during leaching. 
     
     
       54. The process of  claim 52  wherein the Eh is maintained in the range generally throughout the leaching step. 
     
     
       55. The process of  claim 52  wherein the Eh is in the range of 350 to 600 mV. 
     
     
       56. The process of  claim 52  wherein the pH of the lixiviant at the start of the leach is up to about 0.4, and the pH of the lixiviant increases during the leaching step to the range 0.4-2.5 to precipitate iron, as measured by conventional instrumentation. 
     
     
       57. The process of  claim 52  wherein the pH of the lixiviant at the start of the leach is up to about 0.5, and the pH of the lixiviant increases during the leaching step to the range 0.7-2.5 to precipitate iron, as measured by conventional instrumentation. 
     
     
       58. The process as claimed in  claim 52  wherein the lateritic nickel ore comprises magnesium and, prior to exposing the lixiviant to the lateritic nickel ore, the cation is magnesium and the process further comprises adjusting the concentration of magnesium in the lixiviant that is contacted with the lateritic nickel ore so as to essentially prevent magnesium being leached from the lateritic nickel ore. 
     
     
       59. The process as claimed in  claim 52  wherein the concentration of cations having a higher hydration number than hydrogen is selected to reduce the activity of water in the lixiviant. 
     
     
       60. The process of  claim 52  wherein the lateritic nickel ore is exposed to the lixiviant without being subjected to a roasting step. 
     
     
       61. The process of  claim 52  wherein, prior to exposing the lixiviant to the lateritic nickel ore, the lixiviant consists essentially of magnesium chloride and hydrochloric acid. 
     
     
       62. The process of  claim 52  wherein the material is obtained from limonite and saprolite horizons. 
     
     
       63. A process for leaching a value metal from a lateritic nickel ore containing a first metal comprising at least one member selected from the group consisting of copper, iron, manganese, aluminum, zinc and chromium and a second metal comprising at least one member selected from the group consisting of nickel and cobalt, the process comprising:
 (a) contacting the ore with a lixiviant comprising magnesium chloride and hydrochloric acid to produce a value metal-rich leachate and a leaching residue and increasing the pH of the metal-rich leachate to precipitate iron; 
 (b) separating the value metal-rich leachate from the leaching residue wherein the leaching residue includes precipitated iron; 
 (c) increasing the pH of the leachate to obtain a first metal-rich solid fraction and a second metal-rich leachate and separating the first metal-rich solid fraction from the second metal-rich leachate; 
 (d) increasing the pH of the second metal-rich leachate to obtain a second metal-poor leachate and a second metal-rich solid fraction containing the second metal. 
 
     
     
       64. The process of  claim 63  further comprising adjusting the pH of the value-metal rich leachate to precipitate iron as hematite and/or a magnetic iron oxide. 
     
     
       65. The process of  claim 64  wherein the leachate also has solublized therein at least one member selected from the group consisting of iron and manganese and step (c) further comprises subjecting the value metal-rich leachate to oxidation. 
     
     
       66. The process of  claim 64  wherein the leachate also has solublized therein iron and step (c) further comprises treating the value metal-rich leachate to convert ferrous iron to ferric iron. 
     
     
       67. The process of  claim 64  wherein the leachate also has solublized therein manganese and step (c) further comprises treating the value metal-rich leachate such that the manganese is in its tetravalent state. 
     
     
       68. The process of  claim 64  wherein the cation comprises magnesium and the second metal-poor leachate is subjected to recycle steps for recovery of magnesium oxide and hydrochloric acid. 
     
     
       69. The process of  claim 64  wherein, prior to contacting the material, the cation is magnesium and the second metal-poor leachate is treated to produce a solution comprising magnesium chloride and hydrochloric acid that is used as the lixiviant. 
     
     
       70. The process of  claim 69  wherein the treatment step of  claim 68  also produces magnesium oxide. 
     
     
       71. The process of  claim 70  wherein at least some of the magnesium oxide is used as a pH adjustment agent in at least one of steps (c) and (d). 
     
     
       72. The process of  claim 71  in which the treatment step includes partial evaporation and hydrolysis. 
     
     
       73. The process of  claim 63  in which the lixiviant further comprises at least one member selected from the group consisting of (i) at least one additional metal chloride which is added to the lixiviant prior to the lixiviant contacting the material; (ii) at least one additional cation which is leached from the material and (iii) an oxidant. 
     
     
       74. The process of  claim 73  in which additional metal chloride or an additional cation is present. 
     
     
       75. The process of  claim 74  in which the metal of the additional metal chloride and the additional cation is at least one member selected from the group consisting of sodium chloride, potassium chloride, calcium chloride, copper chloride and iron chloride. 
     
     
       76. The process of  claim 74  in which the amount of additional metal chloride and additional cation is 1-25 wt. % of the amount of magnesium chloride. 
     
     
       77. The process of  claim 74  in which the amount of additional metal chloride results from the leaching of the ore. 
     
     
       78. The process of  claim 73  in which an oxidant is present. 
     
     
       79. The process of  claim 78  in which the oxidant is at least one member selected from the group consisting of air, oxygen, chlorine, hypochlorite, chlorite, chlorate, perchlorate, permanganate and peroxide. 
     
     
       80. The process of  claim 73  in which additional metal chloride and oxidant are present. 
     
     
       81. The process of  claim 80  in which the metal of the additional metal chloride and the additional cation is at least one member selected from the group consisting of sodium chloride, potassium chloride, calcium chloride, copper chloride and iron chloride and an oxidant is at least one member selected from the group consisting of air, oxygen, chlorine, hypochlorite, chlorite, chlorate and hydrogen peroxide. 
     
     
       82. The process of  claim 81  in which the amount of additional metal chloride results from the leaching of the ore. 
     
     
       83. The process of  claim 63  wherein the lixiviant has a pH less than about 0.5 and the process further comprises adjusting the pH of the value-metal rich leachate during the leach to above 0.5 to precipitate iron.